2 Answers
2

Not all devices at /dev are physical, some of them are logical and may be temporary needed by kernel/software (and some of them are symlinks, like log_modem -> /dev/ttyACM2).
And, as I see, you have default linux tty count. It's not used (reserved and may be used), but it's no problem.

That's because there are so many devices available. Entries in /dev are not restricted to physical devices, but also include logical ones. You just named one: TTY. You don't really think you've got 63 "connectors" somewhere to attach keyboards etc. to? Also, /dev/random is nothing physical, but rather "software" (a random-number generator provided by the system itself). Same applies to things like /dev/null, /dev/zero, and several others.